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From: clj@ksr.com (Chris Jones)
Newsgroups: sci.space.shuttle
Subject: Re: Definition of "APU"
Message-ID: <3127@ksr.com>
Date: 14 Apr 91 17:24:54 GMT
References: <3331@beguine.UUCP>
Sender: news@ksr.com
Reply-To: clj@ksr.com (Chris Jones)
Organization: Kendall Square Research Corp
Lines: 14
In-reply-to: Tom.Hocking@bbs.acs.unc.edu (Tom Hocking)

In article <3331@beguine.UUCP>, Tom.Hocking@bbs (Tom Hocking) writes:
>
>According to my list of NASA Acronyms, APU stands for "Auxiliary Power
>Unit."  However, the shuttle needs them to generate power any time the
>orbiter is not attached to umbilicals.	
>
The shuttle uses fuel cells to generate its electrical power.  During launch
and landing, it needs auxillary power to move its aerodynamic control surfaces
and gimbal its main engines.  The three APUs provide this power.  They are
turned on 5 minutes before launch, turned off about 12-1/2 minutes after
launch, turned back on about 3 minutes before the deorbit burn (approximately 1
hour before landing) and turned back off again 2 minutes after landing.
--
Chris Jones    clj@ksr.com    {uunet,harvard,world}!ksr!clj